1. Field of the Invention
The present invention relates to a photovoltaic cell using a semiconductor junction and a method of fabricating the same.
2. Description of the Background Art
In recent years, a photovoltaic cell having a junction of an n-type single-crystalline silicon substrate and a p-type amorphous silicon film has been developed. In order to enhance photoelectric conversion efficiency of such a photovoltaic cell, it is necessary to enhance fill factor F.F. while maintaining high short-circuit current Isc and open-circuit voltage Voc.
At the junction of the n-type single-crystalline substrate and the p-type amorphous silicon film, however, there are multiple interface states, causing recombination of carriers to lower the open-circuit voltage Voc.
For this reason, in order to suppress such recombination of carriers at the junction of an n-type single-crystalline silicon substrate and a p-type amorphous silicon film, a photovoltaic cell of an HIT (Heterojunction with Intrinsic Thin-Layer) structure has been proposed in which a substantially intrinsic amorphous silicon film (i-type amorphous silicon film) is inserted between the n-type single-crystalline silicon substrate and the p-type amorphous silicon film (refer to JP 11-224954 A, for example).
This photovoltaic cell receives light on a main-surface of the n-type single-crystalline silicon substrate, generating power inside the n-type single-crystalline silicon substrate. The power thus generated can be taken out of the cell through the electrodes provided on the main surface and back surface.
In the above photovoltaic cell, however, the electrode and the p-type amorphous silicon film on the main-surface side absorbs light, causing the number of photons incident on the n-type single-crystalline silicon substrate to be decreased, resulting in limited power generation efficiency.
In addition, the above photovoltaic cell comprises a large number of layers, causing its manufacturing processes to be complex and manufacturing cost expensive.